Phil Collins on final John Martyn album

Two years after his death, John Martyn's final recordings are to see the light of day. Phil Collins is among the guests on the collection Heaven and Earth, singing on a cover of his song Can't Turn Back the Years.

Folk legend Martyn died in January 2009. While his death ruled out plans to work with jazz musician Pharoah Sanders, Martyn had been recording with producer Jim Tullio, a long-time friend. Tullio is now working with co-producer Gary Pollitt to put Martyn's "last musical testament in order", assembling the posthumous album from an assortment of the singer-songwriter's vocal and guitar takes. "John was a genius," Tullio said. "He made music more naturally than anyone I've ever met, as effortlessly as the way you and I speak."

Martyn's connection to Collins came out of their experiences with divorce. Thirty years ago, both were reeling from the ends of their first marriages; Martyn even "crashed" at Collins's home, and the former Genesis drummer produced Martyn's 1981 album Glorious Fool. "John wanted to do one of Phil's songs to repay him," Tullio said. Before his death, Martyn had begun work on Can't Turn Back the Years, taken from Collins's 1993 solo album, Both Sides. "After John passed, I spoke with Phil and he really wanted to sing on the track," Tullio said. "[Phil] said he had always wanted John to record one of his songs. You can hear the emotion in their voices."

The rest of Heaven and Earth was made using some of Martyn's "favourite back-up singers", with Tullio and Pollitt assembling the sprawling instrumentals. "We didn't do any editing," Tullio explained. "A lot of the tracks are long – even rambling – but we left them that way, as John last heard them. We knew this was it, so we made a conscious decision to keep everything, every morsel."

Heaven and Earth will be released by Hole in the Rain Records on 3 May.